Build and install libpython3.dll

This provides the limited ABI as a separate DLL, forwarding to the
real one. This makes linking with "-lpython3" work.

Fixes #147

Makefile.pre.in

@@ -278,6 +278,8 @@ LIBRARY_DEPS= @LIBRARY_DEPS@
 LINK_PYTHON_DEPS=@LINK_PYTHON_DEPS@
 PY_ENABLE_SHARED= @PY_ENABLE_SHARED@
 STATIC_LIBPYTHON= @STATIC_LIBPYTHON@
+ABI3DLLLIBRARY= libpython3.dll
+ABI3LDLIBRARY= libpython3.dll.a
 
 
 LIBS= @LIBS@
@@ -601,7 +603,7 @@ LIBEXPAT_HEADERS= \
 # Default target
 all: @DEF_MAKE_ALL_RULE@
 build_all: check-clean-src $(BUILDPYTHON) $(BUILDPYTHONW) $(BUILDVENVLAUNCHER) $(BUILDVENVWLAUNCHER) platform oldsharedmods sharedmods \
- gdbhooks Programs/_testembed python-config
+ gdbhooks Programs/_testembed python-config $(ABI3DLLLIBRARY) $(ABI3LDLIBRARY)
 build_wasm: check-clean-src $(BUILDPYTHON) platform oldsharedmods python-config
 
 # Check that the source is clean when building out of source.
@@ -728,6 +730,9 @@ pythonw_exe.o: $(srcdir)/PC/pythonw_exe.rc
 python_nt.o: $(srcdir)/PC/python_nt.rc
  $(WINDRES) $(RCFLAGS) -DORIGINAL_FILENAME=\\\"$(DLLLIBRARY)\\\" -I$(srcdir)/Include -I$(srcdir)/PC -I. $(srcdir)/PC/python_nt.rc $@
 
+python3dll_nt.o: $(srcdir)/PC/python_nt.rc
+ $(WINDRES) $(RCFLAGS) -DORIGINAL_FILENAME=\\\"$(ABI3DLLLIBRARY)\\\" -I$(srcdir)/Include -I$(srcdir)/PC -I. $(srcdir)/PC/python_nt.rc $@
+
 venvlauncher.o: $(srcdir)/PC/pylauncher.rc
  $(WINDRES) $(RCFLAGS) -DPY_ICON -I$(srcdir)/Include -I$(srcdir)/PC -I. $(srcdir)/PC/pylauncher.rc $@
 
@@ -856,6 +861,10 @@ $(DLLLIBRARY) libpython$(LDVERSION).dll.a: $(LIBRARY_OBJS) python_nt.o
  else true; \
  fi
 
+$(ABI3DLLLIBRARY) $(ABI3LDLIBRARY): python3dll_nt.o $(srcdir)/PC/launcher.c
+ $(LDSHARED) -DPYTHON_DLL_NAME=\"$(DLLLIBRARY)\" $(srcdir)/PC/python3dll.c -Wl,--out-implib=$(ABI3LDLIBRARY) -o $(ABI3DLLLIBRARY) python3dll_nt.o \
+ $(LDFLAGS_NODIST);
+
 # wasm32-emscripten browser build
 # wasm assets directory is relative to current build dir, e.g. "./usr/local".
 # --preload-file turns a relative asset path into an absolute path.
@@ -1867,6 +1876,7 @@ altbininstall: $(BUILDPYTHON) @FRAMEWORKPYTHONW@
  if test -f $(LDLIBRARY) && test "$(PYTHONFRAMEWORKDIR)" = "no-framework" ; then \
  if test -n "$(DLLLIBRARY)" ; then \
  $(INSTALL_SHARED) $(DLLLIBRARY) $(DESTDIR)$(BINDIR); \
+ $(INSTALL_SHARED) $(ABI3DLLLIBRARY) $(DESTDIR)$(BINDIR); \
  else \
  $(INSTALL_SHARED) $(LDLIBRARY) $(DESTDIR)$(LIBDIR)/$(INSTSONAME); \
  if test $(LDLIBRARY) != $(INSTSONAME); then \
@@ -2301,6 +2311,7 @@ libainstall: all python-config
  if test "$(PYTHONFRAMEWORKDIR)" = no-framework; then \
  if test "$(SHLIB_SUFFIX)" = .dll -o "$(SHLIB_SUFFIX)" = .pyd; then \
  $(INSTALL_DATA) $(LDLIBRARY) $(DESTDIR)$(LIBDIR) ; \
+ $(INSTALL_DATA) $(ABI3LDLIBRARY) $(DESTDIR)$(LIBDIR) ; \
  else \
  $(INSTALL_DATA) $(LIBRARY) $(DESTDIR)$(LIBPL)/$(LIBRARY) ; \
  fi; \
@@ -2550,7 +2561,7 @@ clean: clean-retain-profile
  fi
 
 clobber: clean
- -rm -f $(BUILDPYTHON) $(LIBRARY) $(LDLIBRARY) $(DLLLIBRARY) \
+ -rm -f $(BUILDPYTHON) $(LIBRARY) $(LDLIBRARY) $(DLLLIBRARY)$(ABI3LDLIBRARY) $(ABI3DLLLIBRARY) \
  tags TAGS \
  config.cache config.log pyconfig.h Modules/config.c
  -rm -rf build platform